Fiber channel switches have been put into practice for controlling transfer of FC frames by using a fiber channel when a storage system performs communications between a server and a storage. “FC frame” is an abbreviation for fiber channel frame. In the explanations below, an FC frame is also referred to as a frame. Also, a fiber channel switch is also referred to as a relay device.
Receiving transmission data from a server, a relay device refers to the destination included in the received transmission data, and transfers the data to the storage specified by the destination that was referred to.
As another related technique, there is a storage system that includes a storage server and an accelerator server. The storage server returns to the accelerator server whether or not block data is stored in a storage device in accordance with a duplication confirmation request from the accelerator server. Also, a technique is known in which an accelerator server performs either an all-block transmission process, which transmits contents identification data of part of block data to the storage server so as to make a duplication confirmation request and transmit all pieces of block data in accordance with the duplication confirmation result, or a partial block transmission process, which transmits respective pieces of contents identification data to all pieces of block data so as to make a duplication confirmation request and transmit to a storage server block data that is not stored.
Also, as another related technique, there is a data transfer system including a host and an interface unit capable of interfacing with a medium that can be accessed by the host. The interface unit includes a storage unit and a control unit. The storage unit holds data written by the host to the medium or data read from the medium. The control unit omits duplicate data writing when data related to an access to the medium from the host exists in the storage unit. Also, techniques are known in which a control unit omits an operation of reading data from a medium by using data in a storage unit when the data related to an access from a host to a medium exists in the storage unit in the case of data reading (For example, Japanese Laid-open Patent Publication No. 2011-175421 and Japanese Laid-open Patent Publication No. 2006-59201).
However, according to conventional relay devices, when for example a bandwidth for a route between relay devices does not have a margin, an increase in the traffic amount makes communications between the relay devices a bottleneck, sometimes leading to a decrease in communication speeds between the relay devices.